Bliss c



B. 0. AMES.

UNBREAKABLE CON CAYO-CONVEX COMPRESSION CRYSTAL.

APPLICATION FILED MAY l2. I917.

Reissued A um-9, 1918.

. INVENTOR.

BY m

fin ATTORNEY.

' T 0 all whom it may concern: 1 Be it known that I, Buss UNITED STATES PATENT OFFICE.

BLISS C. AMES, OFWALTHAM', MASSACHUSETTS, ASSIGNOR TO THE E. INGRAHAM 00., 0F BRISTOL, CONNECTICUT, A CORPORATION.

UNBREAKAEBLE CONCAVO-CONVEX COMPRESSION-CRYSTAL.

Specification of Reissued Letters Patent. 1{eissue(1 Apr, 9, 1918.

Original N0.1,133,780, datedliarch 30, 1915, Serial 1%. 8,603, filed February 16, 1915. Application for reissue filed May 12, 1917. Serial No..168,265.

C. AMEs, a citizen of the United States, residing at Waltham, in the county of Middlesex and State of Massachusetts, have invented a new and useful Improvement in Unbreakable Coneavo-Convex Compression-Crystals 5 and I do hereby declare the following, when-taken in connection with the accompanying drawings and the characters of reference marked thereon, to be a 'full, clear, and exact description of the same, and which said drawings, showing one embodiment of the invention, constitute part of this application, and represent, in- Y Figure 1 an edge view of an unbreakable crystal constructed in accordance with my invention and shown prior tobeiiig placed under compression.

Fig. 2 a plan View thereof. h Fig. 3 a view on an enlarged scale in transverse section of an unbreakable crystal constructed and applied in accordance Withmy invention.

The ob ect of my invention 1s to produce at a low cost an unbreakable or elastic compression crystal.

in its passive or flat state, than the diametor of the undercut groove 4 of-the bezel 5 so that the crystal 2 cannotbe introduced into the groove of the bezel until it has been reduced in diameter by springing it into concavo-convex form. WVhen so sprung, its

edge is introduced into the groove t after.

which the means applied to the disk to spring it into concavo-convex form are released. The disk then immediately recovers itself sufiiciently to seat its beveled edge firmly in the bottom ofthe' groove 4, the compression strain thus set up, holding it in place and at all times compensatmg for con-- traction of the disk. resulting from the shrinkage due to the seasoning of the celluloid. Inasmuch as the disk is always under compression, its edges will always be crowded into the groove of the bezel and, therefore, so tightly fitted therein as to prevent the entrance of any dust or other foreign particles around the edge of the disk.

I am aware that the use of celluloid in the place of glass for watch crystals 'has been proposed and I do not broadly claim the idea, but only my specific crystal made larger in diameter than the supporting ring and thrown into concavo-convex form for its introduction into and retention in the ring. In accordance with the provisions of the patent statutes I- have described the principle of operationof my invention, together: with the structure which I now consider represents one practical embodiment there of. But I desire to have it understood that the device shown is only illustrative, and that in some particulars the invention can be carried out in other ways.

I claim. as my invention:

1. The combination with a rigid supporting ring, of an elastic crystal normally flatdiameter of the said groove into which its edge is inserted after it has been forced into 'concavo-convcx form and thus reduced in virtual diameter to the diameter of said groove whereby the crystal is maintained under compressionin concavo-convex form and so firmly held in place.

The combination with a watch bezel formed with an'annular groove, of a cellu--- loid watch-crystal larger-in diameter than the diamct'erof the -said groove into which its edge is inserted after it has been forced into concavo-convek form and thusred'uced in virtual diameter to the diameter of said groove, whereby the crystal is maintained ;under compression in concave-convex form and-so firmly held in place.

4. A crystal of elastic material distorted by flexure from lti normal form into concavo-convex form, and a rigid supporting ring provided with a crystal receivingpordiamvler of said crystal and upon which it said ring; said crystal being uniformly r0- is mounted while distorted and by it is duced in diameter by distortion into conniaintained in concavo-ronvex form under cavo-convex form to be received and slip- 10 uniform radial compressionstrains. ported by said ring, by means of which it 5 3. T he combination with a rigid supportis maintained in conraio-convex form aning ring of an elastic crystal normally fiat der uniform radial compression strains. and substantially larger in diameter than BLISS C. AMES. 

